Case Study / Waterproofing

Cambridge House, 5 Star Hotel, London

4 Storey basement under a Grade I listed townhouse

Cambridge House Front Elevation, PDP London

One of London’s most iconic buildings is finally on the road to its resurrection, having remained vacant and neglected for almost 20 years.

The scheme is centred around a Grade I listed townhouse, Cambridge House, Piccadilly; the former residence of Henry John Temple, 3rd Viscount Palmerston whilst he served as Prime Minister.

The building also housed one of London’s most exclusive gentlemen’s clubs for more than 100 years, the Naval and Military Club, better known as the In and Out Club.

PDP London Architects were appointed to convert this prestigious and historic building into one of the grandest, luxury 5-star hotels in Central London, as well as seven residences. This large and complex project will also include a lower ground level and three further basement levels to accommodate the spa as well as the back of house and servicing areas that a hotel of this order requires.

Principal Contractor, Deconstruct UK Ltd's redevelopment package involves the deconstruction of the existing structures, retention of the Listed façades and staircase structure, with piled excavation of 4 levels of basements, and subsequent building reconstruction.

Marrying up pure Elegance and Opulence with the challenges of Reliability and Buildability. Nothing is compromised in delivering a stunning redevelopment of a historical space but with the most up to date modern techniques.

Method

This has been a fully collaborative project, the initial design team of PDP and Newton’s have handed over the baton for the projects basement waterproofing element to MacLennan’s own inhouse design team. Who, over the last year and across many workshops, have helped to refine the final and fully guaranteed solution on behalf of the client, Motcomb Estates Limited in line with Deconstruct UK Ltd.

The overall project will be a total redevelopment of the 18,000 sqm site, delivering a truly beautiful place to stay with 102 rooms and 327 covers, for a fully appreciative clientele.

There are several unique challenges within the construction and waterproofing design elements that have been overcome by both Deconstruct and MacLennan’s in delivering something that will be fully fit for purpose and that has buildability at its heart.

The basements are going to be on 4 levels and will be a mixture of Plant rooms, kitchens, Spas, Pools and staff accommodation. The installation of Waterproofing to buildings 1, 2 & 3 will be carried out by MacLennan’s qualified technicians to ensure that they achieve a Grade 3 habitable environment.

The structure will be built as a watertight tank using injectable joins and crack control and some external membranes where deemed necessary.

Internally the waterproofing solution, is a cavity drain membrane installed from floor to ceiling ensuring continuity on each of the levels, with a base drain around the wall floor join and wall mounted inspection ports. This is critical to comply with British Standards and ensures it is maintainable for future servicing of the system. Sumps and pumps with alarms and backup systems will be installed to mitigate the risk of water ingress ensuring the basement remain warm, dry, and habitable.

It is the cavity drain that takes the risk out of the waterproofing mitigating the risk of leaks through minor defects which are inevitable on such a large and technically challenging below ground structure allowing it to be fully serviceable and maintainable.

Result

This is an ongoing project. MacLennan’s fully qualified technicians have been working onsite with Deconstruct UK Ltd since the beginning of 2021.

MacLennan Document all aspects of the work as part of a rigorous Quality control and reporting system. It is attention to detail of every aspect of the work that ensures the project will be carried out effectively.

Maclennan are providing products warranties for all the waterproofing work and the design is covered under MacLennan 10 million PI.

Appointing one contractor, with design liability takes all the split liability out of the project and ensures compliance with all stake holders' requirements.